The most important things in a debate or serious discussion are

1) the ability to agree upon and stay on topic. If the topic continually changes, it's difficult to make progress. It is okay if the topic evolves and changes, but it must be done deliberately and with agreement of those involved.

2) Agreement on the definition of words. Most words are clearly understood, but if new topics are introduced the meaning of the words used to describe those topics should be clearly explained and adhered to.

If all of this is adhered to and someone isn't getting what you are talking about, it's productive to think about how you can explain it better. Finding that path to understanding likely requires stepping back and asking the person questions rather than pouring more information on them for once you understand where they are coming from you can better focus your attention.